1330 SURFACE ANATOMY AND SURFACE MARKINGS 



to its tendon of insertion becomes prominent as a sharp ridge running downw* 

 and medialward. 



On either side of the Biceps brachii at the lower part of the arm the Brachialis 

 is discernible. Laterally it forms a narrow eminence extending some distance up 

 the arm; medially it exhibits only a little fulness above the elbow. 



On the back of the arm the long head of the Triceps brachii may be seen as a 

 longitudinal eminence, emerging from under cover of Deltoideus and gradually 

 passing into the flattened plane of the tendon of the muscle at the lower part of 

 the back of the arm. When the muscle is in action the medial and lateral heads 

 become prominent. 



On the front of the elbow are two muscular elevations, one on either side, sep- 

 arate above but converging below so as to form the medial and lateral boundaries 

 of the anticubital fossa. The medial elevation consists of the Pronator teres and 

 the Flexors, and forms a fusiform mass, pointed above at the medial epicondyle 

 and gradually tapering off below. The Pronator teres is the most lateral of the 

 group, while the Flexor carpi radialis, lying to its medial side, is the most prominent 

 and may be traced downward to its tendon, which is situated nearer to the radial 

 than to the ulnar border of the front of the wrist and medial to the radial artery. 

 The Palmaris longus presents no surface marking above, but below, its tendon 

 stands out when the muscle is in action as a sharp, tense cord in front of the middle 

 of the wrist. The Flexor digitorum sublimis does not directly influence surface 

 form; the position of its four tendons on the front of the lower part of the forearm 

 is indicated by an elongated depression between the tendons of Palmaris longus 

 and Flexor carpi ulnaris. The Flexor carpi ulnaris determines the contoui of the 

 medial border of the forearm, and is separated from the Extensor group of muscles 

 by the ulnar furrow produced by the subcutaneous dorsal border of the ulna; its 

 tendon is evident along the ulnar border of the lower part of the forearm, and is 

 most marked when the hand is flexed and adducted. 



The elevation forming the lateral side of the anticubital fossa consists of the 

 Brachioradialis, the Extensors and the Supinator; it occupies the lateral and a 

 considerable part of the dorsal surface of the forearm in the region of the elbow, 

 and forms a fusiform mass which is altogether on a higher level than that produced 

 by the medial elevation.. Its apex is between the Triceps brachii and Brachialis 

 some distance above the elbow- joint; it acquires its greatest breadth opposite the 

 lateral epicondyle, and below this shades off into a flattened surface. About the 

 middle of the forearm it divides into two diverging longitudinal eminences. The 

 lateral eminence consists of the Brachioradialis and the Extensores carpi radiales 

 longus and brevis, and descends from the lateral supracondylar ridge in the direction 

 of the styloid process of the radius. The medial eminence comprises the Extensor 

 digitorum communis, Extensor digit! quinti proprius, and the Extensor carpi ulnaris; 

 it begins at the lateral epicondyle of the humerus as a tapering mass which is sep- 

 arated above from the Anconseus by a well-marked furrow, and below from the 

 Pronator teres and Flexor group by the ulnar furrow. The medial border of the 

 Brachioradialis starts as a rounded elevation above the lateral epicondyle; lower 

 down the muscle forms a prominent mass on the radial side of the upper part of 

 the forearm; below it tapers to its tendon, which may be traced to the styloid 

 process of the radius. The Anconaeus presents as a triangular slightly elevated 

 area, immediately lateral to the subcutaneous surface of the olecranon and differ- 

 entiated from the Extensor group by an oblique depression; the upper angle of 

 the triangle is at the dimple over the lateral epicondyle. 



At the lower part of the back of the forearm in the interval between the two 

 diverging eminences is an oblique elongated swelling; full above but flattened 

 and partially subdivided below; it is caused by the Abductor pollicis longus 

 and the Extensor pollicis brevis. It crosses the dorsal and lateral surfaces of 



